But interface updates
do meaningfully help many people.
Most people in engineering roles think the job is done when the engineering is done, and the maintenance is unnecessary unless it's necessary for stability or security. That's not limited to software, either. The fact is, to the vast majority of non-developer software users, an improved workflow, more intuitive, or yes, even more attractive interface makes more of a difference than moderate performance upgrades or minor stability improvements.
To a developer, interfaces are a way to interact with with software, like an API for humans. To everyone else, the interface is the software. Old interfaces are as or more usable to you because you have a sophisticated mental model of software and a high tolerance for logical complexity. These dreaded designers' profession is figuring out how people who don't have those things can most easily solve their problem with the tool you built.
Car controls would look a lot different if the engineers maintained control over the available controls without designer input. They might intuitively understand that the array of controls that change fuel injection parameters should only be used in certain instances, but they liked having them right there just in case. When told that they'd just confuse average drivers and should probably be hidden, they might argue, "I explained to my 6 year old nephew how more or less air can affect engine preformance." Multiply that by the dozen internal systems they want to control or get real time data from. A designer world recognize that this would confuse most drivers for little benefit and hide everything but the things most drivers need to find and parse instantly... And they would be met with the same heavy sighs and eyerolls that software designers regularly get from developers.
Designers are in the organization because they can do things that developers can't. They make developers work vastly more useful to the world because the way someone solves their problem is as or more important than it being optimally solved using the smallest amount of available resources with 5 9s of reliability instead of 3.
And that's why, in the overwhelming majority of cases, end-user-facing commercial software with professionally designed UIs and someone looking at UX on a whole will dominate FOSS alternatives while tools targeted at developers and other technical people do as well or better, and the commercial equivalents.